A term that when uttered will usually end a conversation or Facebook thread abruptly. The effect of this is always more pronounced when the subject of the conversation revolves around the now deceased singer/song writer Ronnie James Dio.
Although the possibility of a Hairy Sackett was first postulated by the mathematician Liebniz in 1704, it was not until 1974 that the Indian physicist Sivaramakrishna Chandrasekhar was able to empirically prove it's existance.

Person 1: I have to tell you the story about my enormous cyst before we have dinner.